Bicycle Mechanics - Cones for 8.33 mm axle?
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08-19-11, 11:54 PM
I have a front wheel axle with a 8.33 mm diameter, and can't find anything like it anywhere. Is it possible to get a cone for it? Or can I at least swap in a 9 mm axle set?
You might have a American or British axle. 5/16" = .3125" = 7.94mm. Also 8.33 virtually 21/16" though I don't know if anyone ever used 21/64" axles.
More information might help, like hub markings, thread pitch, bike brand, type, and vintage, and whether it's a solid or hollow QR axle.
If it is a nutted front axle odds are you can use either a 8.5mm or 5/16 axle and cone kit, though front wheels are cheap enough to simply replace unless this one is special, like an original in a restoration project.
08-20-11, 06:27 PM
Thank you Francis. I have not forgotten about my obligation to give you feedback on the Chain-L sample you sent me and will do so soon. The truth is I just recently used it up, despite continuing to commute year-round!
The cone is from a 1982 Trek 613 road bike. I haven't seen any markings on the hub and I'm not certain it is original. I measured it with a high-quality digital caliper and got 8.32 mm. I did consider fractional sizes but didn't think of going to 64ths as you have. The axle seems to be 26 tpi because the threads seem to match another Joyou cone I have labeled 9.0 x 26. Are 8.5 mm axles relatively easy to find? Most of the ones I see are 9.0, 9.5, 10.0, or fractional, plus some oversized. I don't mind chaging the axle set but changing the hub would be an ordeal that I'm not sure outweighs continuing to use the pitted cone.
.......I measured it with a high-quality digital caliper and got 8.32 mm. ... The axle seems to be 26 tpi because the threads seem to match another Joyou cone I have labeled 9.0 x 26....
Are you measuring the ID of the cone thread? If so that solves the mystery. All threads are measured by the OD of the male part, in this case the axle. It sounds like a 9mm x 26tpi axle set and they're very common.
08-20-11, 07:26 PM
8.33 is the outside dimension. Forgot to mention it is a hollow QR. I was also wondering if a 9 mm would fit in the dropouts...
There is no 8.33mm thread. Are you measuring the thread or a stepped down end? You said a 9x26 cone fit, was it radially sloppy or a decent fit.
If the 9x26 cone fit then that's what you need. Maybe you also to check your caliper. Measure a 6mm hex key across the flats to check. It should be between 5.96 and 6mm.
08-20-11, 08:43 PM
There is no step in the axle. I said the threads matched with the 9.0 x 26 cone, but there is radial slop. It is definitely smaller than 9 mm and the slop seems to be more than 0.5 mm. It doesn't thread in the cone at all - I checked thread match by moving the axle to one side while inside the cone.
garage sale GT
08-20-11, 08:57 PM
Could be it's an 8.5. Threaded fasteners are always a bit smaller than the nominal diameter. It's probably a 1mm pitch or 25.4tpi. The radial slop would help to hide small differences in thread pitch such as 26 vs 25.4. Measure the distance between the tops of ten threads (peaks one thru eleven measure ten valleys) and divide by ten and you will know the metric pitch.
Could be it's an 8.5. Threaded fasteners are always a bit smaller than the nominal diameter. It's probably a 1mm pitch or 25.4tpi. The slop would help hide differences in pitch.
Yes, it could be an 8.5mm axle, that was an early guess. Problem is that's a very non-standard size.
At this point I'm wondering if the OP might simply try a 9mm axle to see if it clears the hub shell. If necessary he might open up the center a bit. Thad it's a question of whether he can find cones that fit properly.
Lastly if the fork won't accept a 9mm axle, he could either file the fork tips open, or spin grind the ends of the axle slightly.
08-21-11, 11:07 PM
It seems plausible as 8.5. But even that size seems nigh impossible to find. As far as the cones fitting, as long as they are made for the same size bearing balls I'd think I'd be OK. They are 3/16 balls.
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